1. Field of the Invention
The present invention relates generally to a device for harvesting brine shrimp eggs from a water body. More specifically, the present invention relates to a vacuum device for removing a surface layer of brine shrimp eggs from a body of water.
2. Technology Review
Brine shrimp are primitive crustaceans which normally inhabit bodies of water having high saline contents such as the Great Salt Lake in Utah. They serve as a source of food for many fish. Brine shrimp eggs are remarkable in that they can be dried and stored and hatched years later by returning them to salt water. The ability to stockpile dried brine shrimp eggs for future hatching makes commercial harvesting of the eggs a profitable venture.
Brine shrimp and their eggs conglomerate in floating colonies at the surface of the water. Brine shrimp colonies typically occupy the top quarter-inch of water. The eggs are extremely small in size, such that an ounce of water may contain several million eggs. This floating layer is eventually carried by the wind and the tide to the shore.
Past harvesting approaches have focused on collection after the eggs had been deposited on the shore. Nets or shovels were used to scoop up the thin layer of shrimp eggs and place them into storage containers. This approach was far from effective, however, as the harvester had to depend on the wind and the tide to bring the eggs ashore. Thus, the harvester had no control over when or where the eggs would be deposited.
To deal with the problem of unpredictability, elaborate fencing structures were erected, extending outwardly from the shoreline, to direct incoming shrimp colonies to preselected harvesting sites on the beach. While noticeably more effective in concentrating colonies at predetermined sites, this method was not, however, without its disadvantages. As an initial problem, these extensive fencing structures were understandably expensive. Additionally, this method required that the harvester have access to large areas of shoreline. Finally, the harvester still, had to wait for the right wind and tide conditions to bring the shrimp eggs ashore.
Because of the disadvantages inherent in shoreline harvesting methods, increasing attention has been directed toward methods for harvesting brine shrimp eggs directly from the water. Such methods usually employ a boat or raft equipped with a collection device.
Previous attempts to harvest brine shrimp eggs directly from the water have utilized an assortment of nets or screening devices to skim the eggs from the surface of the body of water. The collected eggs were then transferred from the nets or screens and into storage containers. U.S. Pat. No. 5,042,187 by Bentzley discloses a netting device to collect brine shrimp eggs from a water surface.
There are a number of problems, however, with devices employing netting or screening procedures to remove brine shrimp eggs from water. As an initial matter, netting or screening is generally inefficient because of the very small size of the eggs. With a concentration typically of several million eggs in a single ounce of water, one can easily imagine how great numbers of the eggs pass through conventional net systems avoiding capture.
As the netting or screening device becomes finer and finer, so as to increase the efficiency of extraction of brine shrimp eggs from the water, additional problems arise. It has been found that eggs cling together and solidify when concentrated, thereby becoming very difficult to remove from the netting.
In addition to these problems, the netting device of Bentzley uses paddles which agitate and disturb the layer of brine shrimp eggs at the water surface. As the eggs become dispersed by the paddles, harvesting efficiency decreases.
Because of the problems inherent in extracting brine shrimp eggs with nets and paddles, attempts have been made to pump the egg-rich, top layer of water directly from the body of water into storage containers. U.S. Pat. No. 4,839,062 by Sanders discloses one such method for harvesting brine shrimp eggs. In Sanders, a wedge-shaped concentrating device, comprising a pair of straight-arm booms, is utilized to concentrate a layer of brine shrimp eggs at the surface of a body of water. As the wedge-shaped concentrating device is moved forward with respect to the eggs, the eggs are channeled towards a skimmer which separates the egg-rich layer from the water. The skimmer contains a height adjustment mechanism to selectively position the skimmer at a depth just below the egg-rich layer, usually less than about one inch below the water surface. In this manner, only the egg-rich, top layer of water is directed to the pumping system.
U.S. Pat. No. 4,998,369 by Lamon also discloses a brine shrimp harvester which selectively pumps the egg-rich, top layer of water to storage containers. In Lamon, the harvesting device provides for the gravity flow of the egg-rich layer of water into a collection vessel. The collection vessel is equipped with an adjustable knife edge inlet dam, which serves to allow only the top layer of water to flow into the collection vessel.
Both Sanders and Lamon, however, suffer certain disadvantages in terms of efficiency in harvesting brine shrimp eggs. In particular, both devices are subject the constant fluctuation of water level, making it extremely difficult to extract only a thin layer of shrimp eggs and water from the surrounding body of water. Bodies of water such as the Great Salt Lake have many perturbations in the surface level as an ever present, naturally occurring phenomenon. Such perturbations may take the form of small ripples in the surface to large undulations, or waves, of greater than two feet in height. Obviously, it would be very difficult, if not impossible, to maintain a skimmer or collection device at a constant, predetermined depth just beneath the water's surface when the surface level is constantly changing.
Brine shrimp egg collecting methods which utilize a pumping system to pump the eggs into porous storage containers depend on a proper ratio of eggs to water in order to function effectively. Too much water results in an inefficient collection of eggs in the storage containers. On the other hand, too little water leads to a slurry that is too dry for the pumping system. Thus, it is important that the harvesting device have a mechanism for maintaining a steady input of eggs and water in the proper ratio.
Existing devices have attempted to provide egg/water ratios in this range, but, as previously noted, efforts to provide a continuous and uniform supply of eggs and water in this ratio have met formidable obstacles.
It will be appreciated that there is a need in the art for a brine shrimp egg harvester which effectively extracts the layer of brine shrimp eggs from the surface of the water regardless of the natural rise and fall of the water's surface perturbations. It would be a further advancement in the art to provide a brine shrimp egg harvester which extracts from the surface of a body of water a relatively uniform ratio of eggs to water without agitating the water's surface. Finally, it would be a still further advancement to provide a device that performs these functions in an efficient, cost-effective, commercial manner.